Abstract
BACKGROUND AND OBJECTIVES: Quantitative and operator-independent biomarkers of disease progression are urgently needed in amyotrophic lateral sclerosis (ALS) research. We assess the potential of skeletal muscle MRI as a sensitive and reliable outcome measure for future ALS clinical trials. METHODS: In this longitudinal cohort study, muscle MRI of head-neck, upper and lower limb regions, alongside clinical and functional assessments, were acquired at three time points over the individual maximum observation period (iMOP) of 1 year in 20 patients with ALS and 16 healthy controls. Quantitative MRI parameters cross-sectional area (CSA), volume (VOL), fat fraction, functional rest muscle area and water T2 (T(2m)) were correlated with changes in clinical disease severity (functional rating scales and myometry). RESULTS: Among 20 patients with ALS, 17 completed follow-up. Progressive muscle atrophy (CSA, VOL) was observed at hand (rs=0.66), head-neck (partial η²=0.47) and lower-limb level (thighs: η²=0.56, calves: η²=0.54) over iMOP. MRI changes correlated with leg muscle strength (knee extension: r=0.77; plantar flexion: r=0.78), hand grip strength (r=0.71) and functional rating scales (r=0.68). INTERPRETATION: Our findings demonstrate the effectiveness of muscle MRI as a sensitive neuroimaging biomarker of disease progression in ALS, highlighting its potential application in clinical trials.